Photothermographic diazo material and its method of use for photocopying



United States Patent 3,272,627 PHOTOTHERMOGRAPHIC DIAZO MATERIAL AND ITS METHOD OF USE FOR PHOTOCOPYING Oskar Siis and Herbert Rauhut, Wiesbaden-Biebrich, and

Heinz Schfifer, Wiesbaden-Sonnenberg, Germany, assignors, by mesne assignments, to Keulfel & Esser Company, Hoboken, NJ. No Drawing. Filed Nov. 24, 1964, Scr. No. 413,610 Claims priority, application Germany, Nov. 26, 1963, K 51,457 15 Claims. (Cl. 96-49) The present invention relates to the production of photocopies, and more particularly refers to methods and materials for the production of photocopies.

The production of photocopies according to the diazotype process is well known. According to this process, a support is coated with a light-sensitive layer containing a diazo compound, exposed, and then developed by the action of alkaline substances. In the dry process, the coupling component is coated together with the diazo compound and development is effected by gaseous ammonia. In the semi-wet process, aqueous alkaline developer solutions containing the coupling component are used. In both cases the developing process consists in coupling the unexposed diazo compound with the coupling component to form an azo dye, whereby the image becomes visible.

However, the use of free alkali for development has disadvantages. The solutions used in the semi-wet process contain alkali and readily oxidizable polyhydroxy compounds and thus are not sumciently stable. In the dry process, the gaseous ammonia must be present in excess to insure good development. Thus, special devices are necessary to prevent escape of the gas from the developing equipment.

Attempts have also been made to dispense with the use of free alkali in the developing process and to develop the copies by the action of heat alone. However, the lightsensitive coating must always be acid in order to stabilize the diazo compound, and coupling cannot take place in acid medium. Therefore, thermal development is possible only when the stabilizing acid is removed or the acidity of the coating is strongly reduced to produce the high pH-value necessary for coupling. As stabilizing salt formers, acids which thermally decompose into carbon dioxide or other volatile components have been used. Malonic acid and trichloracetic acid are examples. However, the pH values achieved are not sufficiently high to eilect satisfactory coupling. Contrast is poor.

Finally, attempts to use substances having a heatinduced alkaline reaction or substances yielding alkaline products have been made. In particular, urea has been used for this purpose. When heated to temperatures above 150 C., urea changes into biuret with ammonia being split off. This reaction at 150 to 160 C. proceeds so slowly that development due to the liberated ammonia also takes place slowly. In the art, however, for reasons of economy, short developing times are desired. The comparatively long developing time at these temperatures also involves the risk of damage or burning of the paper support.

Therefore, one object of the present invention is to provide a photocopying material which overcomes the disadvantages of the prior art.

Another object is to provide a method of making a photocopy.

Another object is to provide a method of using said material to produce a copy of an original.

Other objects will become apparent in the course of the following specification.

A process for the thermal development of exposed photocopying material has now been found, which overcomes these disadvantages. The process is characterized by the fact that a photocopying material having a lightsensitive layer containing a diazo compound, a coupling component, and at least one 1-hydroxy-napthalene-8-sulr fonamide is developed by heating to temperatures above C. The sulfonamide has the formula:

in which R represents hydrogen or an alkyl group with one to four carbon atoms, and X represents hydrogen, alkyl, or the group SO NHR, where R represents alkyl, cycloakyl, arylalkyl, or aryl.

In the present sulfonamides, R preferably represents hydrogen, but it may also be a low-molecular weight alkyl group with one to four carbon atoms, for example the methyl, ethyl, propyl, isopropyl or isobutyl group. X preferably represents a low molecular weight alkyl group or the group SO NHR' in which R is generally phenyl or a phenyl radical substituted by a. low molecular weight alkyl group.

The present process is based on the equation:

When heated on the photocopying material, the sulfonamide of Formula A splits off a developing agent such as ammonia or amine with the simultaneous formation of the related sultone of Formula B. This creates the alkaline environment necessary for development directly on the photocopying material. In contrast to the decomposition of urea, the sulfonamides of Formula A split off ammonia or amine almost spontaneously within a very narrow temperature range at or very near to its melting point. In most cases a temperature above the melting point is used in the developing device to initiate spontaneous development of the photocopying material. This considerably shortens the developing time and avoids thermal damage to the copying paper.

In order to develop at low temperatures, compounds with low melting points are used The melting points are greatly influenced by substituents X and R. In particular, low melting compounds have X or R substituted by an alkyl group with one to four carbon atoms.

Still lower melting points may be achieved when mixtures of the sulfonamides with one another or with inert substances which depress the melting point are used. Aromatic hydrocarbons which are solid at normal temperatures are suitable melting point depressants. One such compound is diphenyl.

The lower arrow of the equation indicates a possible way of preparing the present sulfonamides. This possible way is by reacting the 1,8-naphthosultones of Formula B with ammonia or an amine NH R. When carried out with excess ammonia or amine, the phenol group in the 1-position of the naphthalene ring may be converted directly into the related ammonia salt. It is frequently possible to convert a sultone of Formula B where X is hydrogen into its related sulfonamide and then introduce the substituent X by methods known in naphthalene chemistry.

The amounts in which the present l-hydroxy-naphthalene-8-sulfonamides are present in the light-sensitive coatings are not critical, but in order to liberate suffieient amounts of ammonia or amine for adequate development, amounts of one to two times the weight of diazo compound are generally used. There is no upper limit to the amount of sulfonamide added. However, for economic reasons, amounts not higher than five times the weight of diazo compound are generally used.

The degree of suitability of the l-hydroxy-naphthalene- 8-sulfonamides for the present invention may be investigated by preliminary tests, Thus, a particular compound may be heated above its melting point and the presence of volatile amine determined with indicator paper. However, an exposed diazotype paper may also be used instead. The paper is drawn over a vessel provided with a narrow opening and containing the test sulfonamide. When heat is applied, the ammonia or amine is liberated and the azo dye image appears. More expediently, the test compound is brought slowly to its melting point in a reaction vessel containing an unexposed diazotype material and the ammonia or amine formed is transferred to a separate vessel containing the exposed print. The color is rapidly developed when ammonia or amine is liberated at the particular temperature.

The time that the photocopying material remains in the developing zone of many developing devices is less than 60 seconds, and is preferably under 10 seconds.

The developing temperature necessary for the photocopying material naturally varies widely not only with the sulfonamide, but also with the kind of photocopying paper and equipment used. The temperature must be high enough to sufficiently split off ammonia or amine from the sulfonamide, but it must not be so high that the photocopying paper is damaged or that the diazo compound is decomposed. Temperatures above 80 C. are generally required. In the case of sulfonamides melting above 110 0, developing temperatures of not more than 30 C. below the melting point are used. Preferably, developing temperatures are chosen in the range beginning about 30 C. below to 30 C. above the melting point of the sulfonamide. For most copying papers, however, the temperature should not exceed 200 C. For compounds splitting ofi. ammonia or amine at temperatures above 150 C., it is expedient to maintain the developing devices at elevated temperatures so that the heating time is only a few seconds. Plastic and metal foils may be used where higher temperatures are critical.

The light-sensitive coatings always contain a diazo compound and preferably a compound capable of coupling with the diazo compound. Substances suitable for this purpose are those with strong coupling power, such as dihydroxy-naphthalenes andtheir derivatives, phloroglucinol, and compounds which exhibit keto-enol tautomerism, such as pyrazolones, acetoacetic acid arylamides, and dihydroresorcinols. The light-sensitive coatings may also contain inorganic or organic acids for stabilization. Examples are hydrochloric acid, boric acid, formic acid, citric acid, tartaric acid, and 1,3,6-naphthalene trisulfonic acid. Acids which decompose at the developing temperature by decarboxylation, for example, with an increase in pH value are preferred. One example is trichloroacetic acid which increases the rate of development.

The process is carried out by coating paper with a solution containing diazo component, coupling component, and the 1-hydroxynaphthalene-8-sulfonamide. In many cases, it may be advantageous to coat the paper first with a solution of the 1-hydroxynaphthalene-S-sulfonamide, dry it, and then apply the solution containing only diazo compound and the coupling component. The paper may be transparent to heat rays.

Alcohol-water solvent mixtures are generally used. The solutions may also contain one or more of the stabilizing acids, one or more inorganic salts such as zinc chloride or aluminum sulfate, and other additives for accelerating dissolution of the coupling component, for promoting the coupling process (thiourea), or for other purposes (water-miscible organic solvents such as acetone, methyl ethyl ketone, ethylene glycol monomethyl ether). Furthermore, anti-yellowing agents and plasticizers may also be present. The dried photocopying material is then exposed in conventional manner under a transparent original and then heated to the required developing temperature. This takes place by contact with heat, for example with irons or rollers or static hot air atmospheres, for example in drying cupboards or heating cabinets, by heat convection, for example in a hot air stream, or by heat radiation. These measures may also be combined with one another.

The present advantages are that no gaseous alkaline developer and no developer solution containing free alkali are required. The development of the photocopying material takes place spontaneously and at conditions which do not damage the photocopying paper.

The invention is further illustrated by the following examples in conjunction with the table. In the table, structural formulas, names, and decomposition points of some of the 1-hydroxynaphthalene-8-sulfonamides of the present invention are set forth. In the examples, these compounds are in most cases designated only by the appropriate numbers in the table. The preparation of compounds hitherto unknown in the literature is described at the end of the examples. The examples are not intended to limit the scope of the present invention.

EXAMPLE 1 A transparent paper was coated with a solution comprising cc. ethyl alcohol and 50 cc. water together with:

p-Diethylaminobenzene diazonium chloride (as double salt with zinc chloride) 2.0 2,3-dihydroxynaphthalene 2.0 Citric acid 3.0

Thiourea 5.0 Tartaric acid 1.0

1-hydroxynaphthalene-8-sulfonic acid amide 4 sulf-onic acid anilide as ammonium salt (Formula 1 in the table) 7.0

After drying, the sensitized paper was exposed under a transparent original and kept in a heating cabinet for a short time at 120140 C. Blue images with very good contrast were obtained.

When five grams of Formula 1 were used instead of seven grams under otherwise identical conditions, blue images of adequate contrast were still obtained.

When the procedure is carried out without the compound Formula 1, no legible images were obtained.

When the compound of Formula 1 was replaced with an equal amount of one of the compounds of Formulas 2, 3, 4, or 5, images of good contrast were likewise obtained.

The compound of Formula No. 1 was prepared by covering 30 grams of 1,S-naphthosultone-4-sulfonic acid anilide (melting point 147 C.) with cc. of concentrated ammonia water and gently heating on a water bath. The anilide rapidly dissolved and the compound of Formula 1 was precipitated as a crystalline mass. After recrystallization from methanol, 22.5 grams with a melting point of 128 C. (decomposition) were obtained.

The compounds of Formulas 2, 3, 4, and 5 in the table were prepared analogously. When preparing compounds 4 and S, the presence of water was not necessary. These compounds may be prepared by reaction of the related sultones with excess n-propylamine or n-butylamine.

EXAMPLE 2 A photocopying base paper was coated with a six-toe ght percent solution of the compound of Formula 6 in dimethylformamide and dried for about three minutes at 70 C. This was then coated with a solution containing 100 cc. water and:

cc. of concentrated aqueous ammonia to about 65 C. for two hours in an autoclave. The resulting yellow solution G. p Diethylamino benzene diazonium chloride as dew was d1luted with water and made acld to Congo Red with ble Salt with Zinc chloride) 2.0 dil te hydrochloric acid. The compound of Formula 6 ph1oroglucinol 5 precipitated. It was drawn ofi with suction, washed with Ta i id 2 Water and dried. It was then re-precipitated from a di- After the paper had been dried, it was exposed in conmeth-yl formamide-wgter mixture' White crystals i a ventional manner under a transparent original and then memng pomt of 207 (decomposltlon) Wgre Obtalned developed within three minutes at about 140 C. with The compounds of Formuias 7 to 10 were also prepared an iron A heating Cabinet may also be used Copies 10 analogously. When preparing the N-alkylated amides of with brown lines were obtained Formulas 8 and 9, n-propylarnine or n-butylamine was When the compound of Formula 6 was replaced by an used instead of ammonia with the related sultones. equivalent amount of one of the compounds of Formulas It is apparent that the described examples are Capable 7 8, 9 or 10 good copies were likewise obtained 15 of many variations and modifications. All such varia- The compound of Formula 6 was prepared by heating tions and modifications are to be included within the scope 90 grams of distilled 4-methyl-1,8-naphthosultone in 450 of the present inventive concept.

Table Formula Melting Point Sou-NH:

1-l1ydroxynapl1thalenaB-sulphonlc acid amide-t-sulphonic acid anilide (ammonium salt).

128 (decomposition).

1-hydroxynaphthalene-8-sulphonic acid methylamidel-sulphonic acid anilide (methylammonium salt).

144 (decomposition).

1-hydroxynaphthalene-B-sulphonic acid amide 4-sulphonic acid-1% methyl anllide (ammonium salt).

158 (decomposition).

172 (decomposition).

1-hydroxynaphthalene-S-sulphonic acid-n-butyl-amide4-Sulph0nic acid anilide (n-butylammouium salt).

184 (decomposition) HO Sl02-NH2 4-methyl-1-hydroxynaphthalene-8- sulphonamide.

207 (decomposition).

IiI O S02-NH2 -etliyl-i-hydroxynaphthalenc-S- sulphonamide.

186 (decomposition).

T able--C ontinued Formula Melting Point 4-metl1yl-1-hydroxynaphthalenc-S-npropylsulphonamidc.

84-S5 (decomposition).

I'IO SjOr-NH- C4110 4-methyl-l-l1yrlroxynaphthalcnc-Mlbutylsulphonamidc.

95-96 (decomposition).

1 S|Oz-NH 222 (decomposition).

What is claimed is: 1. A heat-developable photocopying material which comprises:

a support; and

a photosensitive layer coated on said support, said layer comprising a photosensitive diazonium compound, a dye-forming coupling component, and at least one 1-hydroxy-naphthalene-B-sulfonamide having the formula:

where R is a member selected from the group consisting of hydrogen and alkyl with one to four carbon atoms; X is a member selected from the group consisting of hydrogen, alkyl with one to four carbon atoms, and the group -SO NHR' where R is a member selected from the group consisting of alkyl, cycloalkyl, aralkyl, and aryl, said sulfonamide being heat-decomposable at temperatures above 80 C. to liberate a developing agent for said layer.

2. A material in accordance with claim 1 in which said sulfonamide is used in amounts at least equal to that of the diazonium compound.

3. A material in accordance with claim 1 in which said sulfonamide is l-hydroxy-naphthalene 8 sulfonic acid amide-4-sulfonic acid anilide.

4. A material in accordance with claim 1 in which said sulfonamide is l-hydroxy-naphthalene-8-sulfonic acid methyl amide-4-sulfonic acid anilide.

5. A material in accordance with claim 1 in which said sulfonamide is l-hydroxy-naphthalene 8 sulfonic acid amide-4-sulfonic acid-3'-methyl anilide.

6. A material in accordance with claim 1 in which said sulfonamide is l-hydroXy-naphthalene-8-sulfonic acid-npropylamide-4-sulfonic acid anilide.

7. A material in accordance with claim 1 in which said sulfonamide is 1-hydroxy-naphthalene-8-sulfonic acid-nbutylarnide-4-sulfonic acid anilide.

8. A material in accordance with claim 1 in which said sulfonamide is coated on said support as a separate layer under the photosensitive layer.

9. A material in accordance with claim 8 in which said sulfonamide is 4-methyl-1-hydroxy-naphthalene-8-sulfonamide.

10. A material in accordance with claim 8 in which said sulfonamide is 4-ethyl-1-hydroxy-naphthalene-8-sulfonamide.

11. A material in accordance with claim 8 in which said sulfonamide is 4-methyl-l-hydroxy-naphthalene-S- n-propyl sulfonamide.

12. A material in accordance with claim 8 in which said sulfonamide is 4-methy1-1-hydroxy-naphthalene-8-nbutyl sulfonamide.

13. A material in accordance with claim 8 in which said sulfonamide is 1- hydroxy-naphthalene-8-sulfonamide.

14. A method of making a photocopy of an original, which comprises the steps of:

exposing to actinic radiation through an original a photocopying material comprising a support coated with a photosensitive layer including photosensitive diazonium compound, dye-forming coupling component, and at least one 1-hydroxy-naphthalenc-S-sulfonamide having the formula:

where R is a member selected from the group consisting of hydrogen and alkyl with one to four carbon atoms; X is a member selected from the group consisting of hydrogen, alkyl with one to four carbon atoms, and the group SO NHR, where R is a member selected from the group consisting of alkyl, cycloalkyl, arylalkyl, and aryl, said sulfonamides being heat-decomposable at temperatures above C. to liberate a developing agent for said layer; and

heating said material to at least 80 C. to develop an image corresponding to the original on the photocopying material.

15. A method in accordance with claim 14 in which the heating temperature is at least 80 C. and not greater than 200 C.

No references cited.

NORMAN G. TORCHIN, Primary Examiner. A. D. RICCI, Assistant Examiner. 

4. A METHOD OF MAKING A PHOTOCOPY OF AN ORIGINAL, WHICH COMPRISES THE STEPS OF: EXPOSING TO ACTINIC RADIATION THROUGH AN ORIGINAL, PHOTOCOPYING MATERIAL COMPRISING A SUPPORT COATED WITH A PHOTOSENSITIVE LAYER INCLUDING PHOTOSENSITIVE DIAZONIUM COMPOUND, DRE-FORMING COUPLING COMPONENT, AND AT LEAST ONE 1-HYDROXY-NAPHTHALENE-8-SULFONAMIDE HAVING THE FORMULA: 